may block as though it had flying Gravitational Shift creatures with flying mtg rules

[SlowFast]

if i have a creature like ancient spider that can block creatures with flying, which bonus does he get from Gravitational Shift?

Or does it change like when he is blocking a flying creature he gets +2/+0 and at other times he gets -2/-0?

[Arix]

Being able to block like it had flying doesn't actually give it flying. It'll always get -2/-0.